I just bought my first Canon last month and spent about a month prior researching bodies. I couldn't understand why they had so many that were so close to each other, for a first time Canon buyer it was very confusing.
Yeh, well for a many time Canon buyer it is very confusing. I have had to do a lot of homework, reading reviews, comparing features.
Canon has slowly made it worse over the years from what started out as 3, maybe 4, distinct lines. The basic essence is still there, the rebel/800d at the lower APC side, the 80D/7DMk II at the higher APC end, and then the 6,5,and 1D at the higher end with Full frame. The problem is they have added a bunch of variations of features to try to appease as many niches as possible. Want a really small light DSLR how about the SL2? Want a mix of features between the 80D and the 800D? how about the 77D? Want a full frame but don't want to spend the money of the 5D, how about the trimmed down version (6D?). But if you look at the direct completion, Nikon has been adding all those minor steps to their lineup too over the years.